A number of different arrangements exist for detecting ground faults in electrical systems. By way of example, U.S. Pat. No. 4,947,126, issued on Aug. 7, 1990 to William E. May, William A. King, and Jerry M. Green, discloses a current measuring circuit which retains the polarity information of signals representative of currents being measured after full wave rectification of the signal. The signal and polarity information may be used to determine whether a ground fault condition exists within the electrical system providing the current.
In one embodiment of the measuring circuit, as applied to a three-phase system, a current transformer associated with each of the phases, including the neutral phase, is used to provide signals representative of the currents in the three phases and the neutral. To determine whether a ground fault condition exists in the system, appropriate circuitry must be provided to condition and properly sum the signals from the current transformers to ensure that a ground fault signal is produced when a ground fault condition exists in the system. In particular, the circuit may retain all of the phase information from the current transformers for the purpose of summing the signals.
In light of the prior art, it would be advantageous to provide a method and arrangement for simplifying the process of vectorially summing the signals which represent the currents in the phases and neutral of a system for the purpose of producing a signal representative of the level of ground fault in a system.